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References

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* This “computed” value was determined as follows: The average a.d. was computed for each case from the data given in Tables IV and VIII. This average a.d. was then divided by the square root of the average number of readings per set, which, while varying somewhat, was very nearly 15.

Tables (9)

Table I

Observer

Type

Precision of single observation

Lummer and Brodhun

Equality

“Mean error” (less than) 0.5 per cent.

Lummer and Brodhun

Contrast (8 per cent.)

“Mean error” 0.4 per cent.

Lummer and Brodhun

Contrast (3.5 per cent.)

“Mean error” 0.22 per cent.

Martens and Bechstein

Equality

“Mean error” 0.59 per cent.

Martens and Bechstein

Contrast (high?)

“Mean error” 0.38 per cent.

Wild

Not given

“Sensitivity” 0.7 per cent.

Kennelly and Whiting

Contrast (high?)

Probable error 0.5 per cent.

Kennelly and Whiting

Equality

Probable error 0.75 per cent.

Kennelly and Whiting

Concentric

Probable error 1.0 per cent.

Millar

Contrast (high?)

Probable error 0.24 per cent.

Edwards and Harrison

Contrast (low)

Average deviation 0.4 per ct.

Table II

Color

Observer

Number of sets examined (10 to 20 settings each)

Average a.d. of a single observation

Average maximum deviation

Carbon

C

25

0.301

0.780

Carbon

R

44

.310

.828

Carbon

T

97

.314

.825

Mean

0.308 per cent.

0.811 per cent.

Blue

C

67

.327

.830

Blue

R

138

.318

.780

Blue

T

74

.299

.723

Mean

.315 per cent.

.778 per cent.

Yellow

C

40

.306

.824

Yellow

R

33

.342

.912

Yellow

T

71

.309

.813

Mean

.319 per cent.

.850 per cent.

Mean of all

.314 per cent.

.813 per cent.

Table III

Photometer: Lummer-Brodhun Contrast.

Color difference (in terms of temp. difference)

Observers

Total number of sets examined

Average a.d. of one setting

Average maximum deviation

Per cent.

Per cent.

20°–25°

C, F, G, H, K, R, S, T.

23

0.393

1.25

20°–30°

C, F, G, H, K, R, S, T.

21

.386

1.04

20°–35°

C, F, G, H, K, R, S, T.

24

.404

1.11

Table IV

Photometer: Lummer-Brodhun Contrast.

Color difference

Observers

Total number of sets examined

Average a.d. of one setting

Average maximum deviation

Per cent.

Per cent.

None:

Group A:

Carbon-carbon

C, R, T

18

0.345

0.78

Carbon-carbon

Group P:

B, F, G, J, K, S, W

42

.58

1.60

Carbon vs. tungsten

Group A

6

.60

1.95

Carbon vs. tungsten

Group P

14

1.36

3.40

Carbon vs. gas-filled

Group A

18

1.00

3.45

Carbon vs. gas-filled

Group P

42

1.95

5.20

Table V

Showing Precision as a Function of Flicker Speed

Speed (light cycles per second)

Total number of sets examined

Average a.d. for one setting

Average maximum deviation

Per cent.

Per cent.

18

5

0.99

2.6

15

5

.95

2.1

12

5

.91

2.25

9

5

.94

2.5

6

5

1.32

375

Table VI

Flicker Photometer.

Color difference

Observer

Total number of sets examined

Average a.d. for one setting

Average maximum deviation

Per cent.

Per cent.

Carbon-yellow

B

22

1.12

2.88

Carbon-yellow

C

38

1.19

2.78

Carbon-yellow

F

8

1.22

2.87

Carbon-yellow

K

8

1.45

4.13

Carbon-yellow

M

7

.70

1.89

Carbon-yellow

N

9

.72

1.64

Carbon-yellow

R

36

.54

1.54

Carbon-yellow

S

8

1.48

3.84

Carbon-yellow

T

4

.96

2.21

Carbon-yellow

V

9

1.32

3.40

Mean

1.07

2.71

Carbon-blue

B

22

0.88

2.27

Carbon-blue

C

28

.73

1.74

Carbon-blue

F

8

.88

2.27

Carbon-blue

K

8

1.06

2.86

Carbon-blue

M

7

.74

1.66

Carbon-blue

N

9

.82

2.16

Carbon-blue

R

31

.47

1.09

Carbon-blue

S

8

1.10

3.04

Carbon-blue

T

4

.94

2.51

Carbon-blue

V

9

1.01

2.23

Mean

.86

2.18

Table VII

Comparison of Flicker with Equality-of-Brightness Measurements in 2° Field

* This “computed” value was determined as follows: The average a.d. was computed for each case from the data given in Tables IV and VIII. This average a.d. was then divided by the square root of the average number of readings per set, which, while varying somewhat, was very nearly 15.